Conventionally, as disclosed in Japanese Patent Laid-Open No. 2005-110202 (JP '202), a vehicle periphery monitoring apparatus having a wide-angle lens camera is proposed for providing a driver of a subject vehicle with a wider field of view, which has a view angle of at least 180 degrees. Though such an apparatus has a very wide view angle, a trade-off of having a smaller image size for an object captured in a corner/periphery of a captured image cannot be avoided. More practically, when a vehicle backs up, the driver of the subject vehicle, even though staring at the captured image of a rear view of the vehicle, cannot notice/recognize an object captured in the corner of the captured image that is very small, since the driver's attention is naturally drawn to a nearby vehicle parking on the left/right of the subject vehicle with minimum clearance.
Therefore, for example, a monitoring apparatus that emphasizes a moving object on a display unit is proposed in Japanese Patent Laid-Open No. 2005-123968 (JP '968), which emphasizes the moving object after cropping such object from the captured image. In JP '968, the emphasizing scheme of the moving object is disclosed as a calculation of an optical flow of feature points in the captured image and a formation of a motion vector for each of the feature points, enabling a cropping of the moving object from the captured image. The cropped moving object in a dead angle of the subject vehicle Is then displayed in an emphasized manner on the display unit, thereby allowing the driver of the subject vehicle to easily notice/recognize such a dangerous object in the dead angle.
However, extraction of the motion vectors from the captured Image by processing an image based on a calculation of the optical flow, as provided in JP '968, requires a huge processing load. Thus, an accurate cropping in response to the motion of the moving object may only be enabled by a separate/dedicated processor for having processing results in a timely manner.
Therefore, as shown in FIG. 9, in some recently-developed image capturing apparatus, a detection line L extending horizontally in a left-to-right axis is set in the captured image for capturing an outside periphery of the subject vehicle for the detection of the moving object. A detection area for detecting the moving object is narrowed to such detection line L.
Specifically, by setting the detection line horizontally along the left-to-right axis of the captured image, the moving object may be detected based upon a brightness change of the pixels along the detection line and a determination threshold (i.e., a parameter) for determining whether the brightness change of the pixels is caused by the moving object.
However, when the moving object is detected based on a configuration that detects the moving object according to the brightness change of the pixels along one detection line, a vertical size of the moving object is not considered in the captured image. In particular, a false detection of a moving object may be possible. For instance, fallen leaves or a noise in the image may be detected as the moving object, which should not be detected. Such false detection leads to an inaccurate device.